Enzymes I
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Enzymes are _______
catalysts
why is it important to study minor components in foods?
they are major attributes to food nutrition defines the way we process foods
what is an enzyme?
o Most enzymes are proteins in nature with catalytic functions o Their molecular weights and chains are usually smaller than other proteins such as collagen (100-400kDa), myosin (200kDa), etc. trypsin (20kDa), amylase (40-50kDa)
what are the functions of enzymes?
o Decrease the speed of biological reactions by reducing the activation energy (Ea) in organisms. o Enzymes are biomolecules that enable biological reactions to proceed at perceptible rates in living organisms (animals, plants, microorganisms) o All these organisms have the same functional classes of enzymes to enable them carry out the same kind of metabolic processes.
Why is it important to study enzymes in food chemistry?
o Desirable effect: processing o Undesirable effect: rancidity, browning…
protein nature of enzymes
influence of H+ or OH- influence of proteases response to typical protein tests evidence from X-ray crystallography
Protein nature of enzymes: influence of H+ or OH-
Enzymes can be hydrolyzed by dilute acid or alkali, just like proteins, to form free amino acids or low molecular weight peptides.
Protein nature of enzymes: influence of proteases
Enzymes can be broken down by proteases, just like proteins, to form AA or peptides with the participation of water.
Protein nature of enzymes: response to typical protein tests
Enzymes can respond to typical common protein tests, such as: • ninhydrin test, • biuret test, • Lowry test, • BCA test.
Protein nature of enzymes: evidence from X-ray crystallography
Enzymes are composed amino acids liked together by peptide bonds, just as it occurs in protein, by X-ray crystallography.
Holoenzyme
complete enzyme with functional activity
Proenzyme
not functioning, needs to be activated
Apoenzyme
protein part of the enzyme
Prosthetic group
essential non-protein part of the enzyme. Mainly metal ions such as Co, Fe, Zn..
Coenzyme
non-protein part, helps the functioning. Can be proteins or minerals.
Give examples of the enzymes that are composed only from holoenzyme. Hint: these enzymes are just made up of proteins
trypsin, pepsin, chymotrypsin, renin
Some enzymes need a ____ in order to be able to function. These ions can be found on the active sites, they are bound to the protein very tightly.
prostethic group
Give examples of enzyme that cannot function without the prosthetic group
Polyphenol oxidase – Cu (in the active site or close to the active site) Peroxidase – Fe (combines with the substrate)
What makes an enzyme different than other common proteins?
o They have catalysis function o Enzymes have active sites
What are active sites in enzymes?
o Active site is a region where that substrates binds and transforms into products. o Binds with substrates (S) o Transform S to products (P) o As a result of these 2 events, new bonds formed or broken to form the products
General features of active sites
o Small o Crevices/Clefts o 3D o has two parts: binding site and the catalytic site where the catalytic reaction happens
Active site has two parts ____ and ____
binding site and the catalytic site where the catalytic reaction happens
Active sites have two functions
binding and transformation
What is the relation between binding and transformation of an enzyme?
o Binding of S precedes transformation o Not all binding lead to transformation o No transformation without binding